Unable to Paste Image into Rich Text field

I am working on an XPage application with a rich text field on a page. In the application, I am unable to paste the image (even plain text) in rich text field.

The application is deployed in two servers (master copy on one server, and a replica copy on another server). Everything is working fine in master copy of database (on master server), but in the replica copy of the application, paste images and texts is not working.

When trying to insert image through 'Insert Image' tool bar button of rich text control, popup gets opened but nothing works in the popup (neither upload button, not ok, cancel or close buttons works here)

Configuration settings of both servers are almost identical. As per my knowledge, the only difference is that, in maser server, session based authentication mode is configured, and in the server having replica copy, basic authentication mode is configured.

I haven't 100% confirmed this yet, but I just ran into this issue, our staging enviroment is running v9, production is 8.5.3, and I believe it is the dojo version that is the issue. We use a Staging env' that is similar to our prod'n env: cluster, reverse proxy, SSO, etc., the only "main" diff at the moment is Domino verison. THe funny thing is, I pastyed this image below, which is exactlky what we are taklking about... :).